a) Field of the Invention
The invention is directed to a method for determining the diameter of optically accessible blood vessels based on digital images showing the blood vessels and their environment. The method according to the invention is provided in particular for application to the fundus of the human eye but is not limited thereto.
b) Description of the Related Art
The vessel diameter of blood vessels and changes in the vessel diameter due to provocation or stimulation of the metabolism are an important physiological measurement quantity.
Known methods for determining the vessel diameter in optically accessible vessels, for example, in those of the oculus fundus, are often planimetric methods which are implemented in a manner suitable for the evaluation of digitally recorded images or digitized images in image processing programs.
A method of this kind is known, for example, from DE 196 48 935 A1, which determines the vessel diameter based on vessel edge acquisition as the distance between photometric vessel edge centroids formed by interpolation with corrected oblique position of the vessel edges. This method achieves a reproducibility that enables significant individual detection of regulatory changes.
However, a disadvantage arises from the geometric measurement of the vessel diameter based on digital images because the measuring accuracy is limited by the resolution of the raster of digital image points. When the vessel diameters reach an order of magnitude in the range of a few image points, this increases the error in the geometric measurement.